Telephone system.



PATENTED AUG. 1 1908.

'0. L. GOODRUM. TELEPHONE SYSTEM. APPLICATION FILED JULY 31 1903.

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CHARLES LANE GOODRUM, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE DEAN ELECTRIC COMPANY, OF ELYRIA, OHIO, AOORPORA- TION OF OHIO.

, TELEPHONE SYSTEM.

, Patented Aug. 18, 1908.

Application filed July 3i, 1903. Serial No, 167,707.

To all whom it may concern:

Be it known that I, CHARLES LANE Goon- .RUM, a citizen of the United States, residing same.

My invention relates to telephone exchange systems, and has for its object the production of a system such that all the exchange functions may be more perfectly periormed by simpler apparatus than heretoore.

In tcIephone-exchange systems, even of small size, it is .now customary to employ a centralized or common source of electrical energ from which current is derived for use at the subscribers stations as well as at the central station. Such centralization of the power-supply hasrendered it possible to employ automatic signals throughout-that is, signals which do not require separate acts specially performed by subscriber or operator for their actuation or restoration to normal, but which respond directly to conditions as they are produced or changed in initiating, setting up, responding to, and terminating a conversational connection. Thus in modern systems a subscriber performs no special "act in callin but simply removes his receiver from its 00k and places it to his ear ready to converse and to listen, givin no thought to the signal, which neverthe ess, has responded to his closure of the line-circuit. When the operator has set up the desired connection, she need use no switch to ascer tain the wishes of the subscribers or thecondition of the lines by listening or otherwise, for each cord-circuit is provided with telltale signals, (usually two. in number, one for each subscriber,) which respond faithfully to each change in condition of the line as it is a'fiected by the use or disuse of the subscribers talking apparatus. Such systems are called supervisory systems, the automatic signals affording an opportunity for constant and perfect supervision simultaneously of all the connected lines controlled by each operator.

In most common battery systems the lines are normally extended when in disuse to the main-battery bus-bars through the windings of the line-signal magnet or relay and through the contacts of another relay,

which is connected to contacts in the jack or jacks to be energized when a plug is inserted therein and thereupon cut off the extension of the line, whereby the line-signal, being deprived of current,'is restored to its normal condition. The cut-off relay thus employed requires a three conductor cord; but this disadvanta e is considered preferable to cutting off in the jack, which is the alternative method. I employ neither method, but avoid the disadvantages of both by using shunts, closed when the plugs are inserted.-

Upon'reading the following description it Will be apparent that the signalsI describe as supervisory signals might very well have other funotions'for instance, replacing linesignals or trunk-signals. I desire it to be expressly understood that I consider myself to be the originator of this type of signal controlled by the differential action of divisions of a single battery or generator or of separate units employed in the relations pointed out with the regard to the supervisory signals herein. .As it would not require more than the skill of a trained electrician or telephone engineer to make the changes required, I consider that all such changes are well within the scope of my invention.

Other features of my invention will appear hereinafter from the description and claims.

In the accompanying drawing, wherein similar parts are pointed out by the same characters throughout, Figures 1 and 2 are diagrams illustrating my, invention.

In the drawing, A and B represent two subscribers stations, each connected to the central office C by line wires 1 and 2. As these stations are alike in their equipment and connections, I will describe the station A for both. At this station the line-Wires 1 and 2' are-normally connected for alternating currents through the condenser P, ringer Q, and switch-hook H, the hook being down. When the receiver is removed from the hook,

the bell oi ringer circuit is broken and the? line wire. 1 is connected to the bus-barf39 through the choke-coil Sand wires-2 7 and A test ring or'thimble 6 is also provided in,

the 'jack, and this is connected, as shown, to the same thimble in all the multiple jac-ks of the same line and by stem 5 and wire 29 to a point as, intermediate the line-relay 9 and the choke-coil 7. The splring 4 is so positioned with regard to the t imble 6, that when a plug 'is inserted the sleeve thereof will cross,

the spring-and thimble to ether. The-purpose of thisfwill be pointe out later.

- The resistance of the coil 8.1 usually make about two hundred ohms, that of the relay 9 I make one thousand three hundred ohms, and of the coil 7 one thousand two hundred ohms. The relay 9 controls an armature 24,

. which closes on a contact point 25, connected lays R- R are provided.- I will describe the and 14.

by wire 26 to the bus-bar 39. The armature or its equivalent, which may be-a twin contact to 25, is connected by wire 16 to the line-signal lamp 10 andthence by wire 17 to the other side of battery at bus-bar 38. It will be understood that these wire connections are not necessarily carried individually to the power-board, but that com-. mon wires may form continuations of the bus-bars.

The multiple jacks (represented by J) are in every respect duplicates of the jack J and are connected in parallel therewith to the wires 1, 2 and 29.

Interconnection of the lines for conversation is effected throu h the cord-circuit 181 9 2323. This cor a circuit terminates in plugs M M and is conductively divided, but inductivel completed by the condensers 13 or continuous currents, therefore, acomplete conversation-circuit consists of two independent sections, which are fed separately. Each plug M or M is provided with a tip-contact 20, connected to one side 18 or 19 of the cord, and with a sleeve-contact 21, eonnected with the other side 23 of the corc For each cord circuit two supervisory reone R for both. This consists in the present case of a horseshoe permanent magnet 11, having windings upon its two oles of 'approximately seven hundred an fifty ohms reslstance connected by wires 22 and 34 to the cord-conductor 23 on one side and to bus-bar 340 on the other. This bus-bar 340 is a third bus-bar of the main battery, being connected thereto at such a point thatthe difference of potential between it and the bus 38 will be much less than that between it and bus 39, the former being, for instance,

where the total voltage of the main battery is forty. All the su ervisory relays are confrom bus 38'to a lamp 1 2, and so by wire 32 to the contact-point 31 which lies in the path of the armature '36. armature a normal bias to the right; but ity is obvious that this may be accomplished in other'ways, and, in fact, the entire construction of the relay may be varied in a hundred ways without departing from the spirit of the invention. I reserve to'myse'lf the right to make this relay in any convenient "way therefore.

Theo eration of, the system so described is as follbws: The subscriber A,-I will su .ose, wishes to converse. with subscriber e removes the receiver R from the hook H, which thereupon rises and closes the circuit Its purpose A spring 37 gives the current from the main battery to pass Y through the following circuit bus-bar 39, wire 27, choke-coil 8, wire 28, line wire -1, talking set R T H, line-wire 2, wire 15, relay 9, choke coil 7, wire 30 to bus-bar 38. This energizes the relay 9, which thereupon attracts its armature 24 and closes the local-line lampcircuit as follows: bus-bar 39, wire 26, point 25, armature 2,4,wire 16, lamp 10, wire 17 to bus-bar 38. The lamp 10 then lights, informing the operator of the call. sponds by inserting the answering plug 'M,

by the mere insertion of which three results.

are produced, viz: The cord conductors are brought into connection with the line-wires, the relay 9 is shunted by the wire 29, stem 5 of the testthimble, the thimble itself, 6, and the sleeve of the plug to spring 4, thus caus ing the relay-armature to fall away and ex tinguish the lamp 10, and the su ervisory relay is connected to the jack-t imble 6 through the sleeve conductor 23 of the cord by the following path to battery: wire 22,

cord-conductor 23, plug-sleeve 21, vjack- She re-- thimble 6, stem 5, wire 29, coil.7, wire 30 to: bus 38 and battery B, through the upper division 40 of the battery to the bus 340, and by wire 34 back to the relay. This current.

flowing throu h the relay-coils under an electromotive force of, say, six volts if unopv posed would suffice to overcome the s ring 37 of the armature '36, drawing the atter over to the left and closing on the contact31,

this lighting the lamp 12. by current flowing; in circuit 39, 35, 36, 31., 32, 12,33, 33 to.bat-

tery. The lighting of the lamp in answering thec'all is prevented, however, by an .opposing current that flows in the following circuit:

.termine if the wantedline is free.

bus-bar 39, wire 27, coil 8, wire 28, line-wire 1, subscribers talking set (which is iri'service line-wire 2, spring 4, sleeve or thimble 6, sleeve of plug 21, wire 23, wire 22, windings of relay R, wire 34 to bus-bar 340, and so to battery. e thus have a divided battery connected so that there are opposed electromotive forces through the windings of the relay R, and as they are unequal the resultant current is in a direction to reinforce the spring 37 and not to oppose it. Thus the supervisory lamp does not light for the ca ling-line. Having received the number wanted, the operator proceeds to test to de- This she does by throwing over the listening key K to listening position, and thereby bringing her head-phone into connection with the tipof the calling-plug M on one side by the path 51,K, 52, 19, and 20, and into connection with the bus-bar 38 ofthe main battery on the other side by the path 53, choke-coil 54, to bus 38. Now when the ti 20 is touched to the thimble 6 of the wanted line if the subscriber has called from station B and has not yet been answered a circuit will be com-' pleted from the ti through the thimble 6 to nc and back an by conductor 28, coil 8,

and wire 27 to the bus-bar 39, the current flowing in this circuit producing a characteristic busy click in the operators ear. If,

' the multiple jack already in use and over the T as a matter of course.

sleeve of the plug therein and its cord conductor 23 to the polarized relay R and to bus-bar 340. If a cord at another section has already been brought in to connection with the wanted subscribers line and he has answered the call, then both the paths traced will be available .and the click will be heard, If the line is idle, however, no click can be obtained, because the tip 20 and sleeve or thimble 6 will be at the same potential.

It will be observed that connection is .made to but one side of the cord fromthe' battery B, and a word of explanation is here in place concerning the current-supply for talking. The battery has the permanent branches 27 and 30, including the chokecoils 8 and 7, respectively, by which direct current is fed to the linesin parallel, the

the line-supply.

scri

While I have. described the supervisory relays in my system as of the polar type, I do not claim the same specifically in combination with the other elements of the system, such combination, and the principle ofjreversed electromotiveforces upon which it depends being specifically aside from the present invention, although included thereunder. As I have reviously stated, these relays may be of or inary neutral type, the intermediate bus-bar of the battery being adjusted so that in any case the insertion of a plug and the simultaneous closure of the subtend it to include the divided battery principle as applied to line signal relays, as well as to supervisory relays. In the ordinary form of relay the armature'is normally biased away from the poles of the magnet by a retracting spring. This corresponds to the polar biasof'the relays I have described. Such a relay if included in the line connection between the jacks and the battery, would respond to the current flow when the subscriber closes the line circuit, by holding up its armature, the relay connection being always to the intermediate bus-bar and the subscriber therefore closing through onehalf or division of the battery. When the o erator plugs in she brings the other half of t e battery into circuit by connecting its opposite end cell to the relay side of line outside of the relay. We have therefore, in such case, the full battery from end to end bridged across the line, with the line relay connected from its intermediate point around one side or division of the battery. In a figure this could be graphically represented by a circle divided by a diameter, with onehalf of the battery on each side of the diametral line, and the line relay in the diametral line, as shown in Fig. 2. As long as both arcs of the circle are com late, the relay receives no current, unless t e two'portions of the battery be made une ual, as in the case described, WhiOh-WOllld e required where the lines were of unequal length and connected to different points on the battery in order to maintain'e qual potentials on all line terminals. In such case, any marginal current is compensated for. by strong or weak adjustment of the tension of the retracting sprin .In the figure mentioned, one portion of t e are represents the subscribers line, and the ot er portion represents the cord-circuit connection to the battery.

I believe I am the first to suggest and to devise practical means of applying the sug-. 'estion of a divided battery, with means uner the control of a subscriber to produce a current flow from one division of the battery, means under the control of another subers line will produce a balance or an apscriber or an operator to control the. current flow from the other half or division of the I battery, and a translating device common to both halves ordivisions, whereby the translating device may be energized, neutralized,

' again deenergized, and again neutralized, if

claims all formsof apparatus and circuits Whatever by which the principle enunciated is applied in the general manner and for the general pur oses stated.

Having-t us described my invention, what I claim, and desire to secure by Letters Patent of the United States is 1. In a tele hone exchange system, the, combination or the following instrumentali-' ties: a plurality of substations and a central station, with metallic line circuits interconnecting them, a plurality of testing terminals for each line connected together in multiple, an operators cord circuit with terminal plugs for interconnecting the lines, a main battery permanently connected in its entirety across the central oflice terminals of each line, a line signal magnet connected in one side of each line, a normally incomplete shunt for each I. line signal magnet terminating on the testing terminals,- a supervisory signal magnet con nected from the sleeve side of the operator's cord to an intermediatepoint 0n the main battery, sprin jack contacts for each line associated Wit the testing terminals and adapted to cooperate with the respective contacts on the plugs to simultaneously shortcircuit the line signal magnet and toconnect the supervisory signal magnet so that itwill be exposed to a potential difference through the line circuit which will maintain it in an inoperative or non-signaling condition While the line is in use, and an operators test set connected from the tip side of the cord to the sleeve side of the battery, substantially as described.

2. In a telephone exchange system, a plurality of substationsand a central station with" metallic line circuits interconnectin them, multiple jacks for each line, each j ac having a tip and sleevespringand a testing terminal, a'line relay connected in one side of each line beween the test terminal and the sleeve s ring, a two-conductor cord'with ter- I minal p ugs for interconnecting the lines, a '7 main battery permanently connected in its entirety across the terminals of each line, an

electromagnet and a connection therethrough from an intermediate point-of the battery to the sleeve side of the cord, and an o erators test set connected'from the tipsi e of the cord to the outside or main terminal of the battery which is connected to the sleeve side of the line, whereby the insertion of a plug in any multiple jack will simultaneously raise the potential of-its multi le test terminals with respect'to the tips 0 the testing plugs and short-circuit the line relay, substantially as described.

3. In a telephone exchange system, a plu- I rality of subscribers stations and a central station with a line circuit interconnecting them, a source of current connected'to the line and a signal magnet connected to said source at a point intermediate its terminals so. as to divide it, means controlled by each subscriber to close the circuit through the sigminal therefor connected to the outside of the battery, whereby the closure of the magnet circuit may be utilized for indicatinithat the line is busy, substantially asdescri ed.

In witness whereof I have hereunto set my hand this 30th day of July A. D. 1903, in the presence of two subscribing witnesses.

' CHARLES LANE GOODRUMQ- Witnesses:

EDWARD E. CLEMENT, M, S. LEWIS. l 

